We propose to analyze the mechanism of control of cell differentiation and morphogenesis in the cellular slime mold Dictyostelium discoideum, with particular emphasis on the role of cyclic AMP and calcium ion. Our approach is to suppress normal differentiation and morphogenesis by submersion of the slug stage under water. We implant into the slugs Sephadex particles which serve as sources of cyclic AMP, calcium ion, or other possible control agents. Our earlier work has supported the hypothesis that cyclic AMP is a key control agent in stalk cell differentiation and stalk morphogenesis and also, directly or indirectly, in spore cell differentiation. We were led to propose a general hypothesis concerning the control of the developmental pattern by relative oxygen levels and respiration rates in the slug. It is our intention to test this hypothesis. We also intend to carry out the study of anterior-posterior response differences in the slug, and a thorough investigation of the role of calcium and other ions in the induction process. Another of our aims is a careful and precise study of spatial relationships between implanted sources and induced stalk cell clusters and stalk sheaths. We plan to carry this out by histological analysis of intact slugs, using both light and electron microscopy. We also plan to study these questions by microcinematographic analysis of development in slugs crushed under mineral oil. It is hoped that these investigations will shed further light on these basic developmental problems.